Abstract
Trace element concentrations in toenail clippings have increasingly been used to measure trace element exposure in epidemeological research. Conventional methods such as inductively coupled plasma mass spectrometry (ICP-MS) and high-performance liquid chromatography ICP-MS (HPLC-ICP-MS) are commonly used to measure trace elements and their speciation in toenails. However, the impact of the removal of external contamination on trace element quantification has not been thoroughly studied. In this work, the microdistribution of trace elements (As, Ca, Co, Cu, Fe, K, Mn, Ni, Rb, S, Sr, Ti, and Zn) in dirty and washed toenails and the speciation of As in situ in toenails were investigated using synchrotron X-ray fluorescence microscopy (XFM) and laterally resolved X-ray absorption near edge spectroscopy (XANES). XFM showed different distribution patterns for each trace element, consistent with their binding properties and nail structure. External (terrestrial) contamination was identified and distinguished from the endogenous accumulation of trace elements in toenails─contaminated areas were characterized by the co-occurrence of Co, Fe, and Mn with elements such as Ti and Rb (i.e., indicators of terrestrial contamination). The XANES spectra showed the presence of one As species in washed toenails, corresponding to As bound to sulfhydryl groups. In dirty specimens, a mixed speciation was found in localized areas, containing AsIII–S species and AsV species. ArsenicV is thought to be associated with surface contamination and exogenous As. These findings provide new insights into the speciation of arsenic in toenails, the microdistribution of trace elements, and the effectiveness of a cleaning protocol in removing external contamination.
| Original language | English |
|---|---|
| Pages (from-to) | 4039–4047 |
| Number of pages | 9 |
| Journal | Analytical Chemistry |
| Volume | 96 |
| Issue number | 10 |
| Early online date | 29 Feb 2024 |
| DOIs | |
| Publication status | Published - 12 Mar 2024 |
Bibliographical note
Open Access via the ACS agreementThis research was performed on the XFM beamline at the Australian Synchrotron, part of ANSTO. Special thanks to Prof Dr Rajiv Chowdhury (University of Florida, Miami, USA) for the financial and academic support as scientific manager of the BRAVE study while at the University of Cambridge (Cambridge, UK). We gratefully acknowledge the contributions of all BRAVE study participants, the scientific staff of the collaborating centre icddr,b and the recruitment centre NICVD in Bangladesh. Epidemiological fieldwork in BRAVE has been supported by grants to the coordination centre for BRAVE at the British Heart Foundation (BHF) Cardiovascular Epidemiology Unit (CEU) at the University of Cambridge. The CEU is underpinned by programme grants from the: BHF (RG/13/13/30194; RG/18/13/33946), UK Medical Research Council (MR/L003120/1) and NIHR Cambridge Biomedical Research Centre (BRC-1215-20014; NIHR203312) [*]. *The views expressed are those of the authors and not necessarily those of the NIHR or the Department of Health and Social Care.